The present invention relates to an assembly composed of a vacuum pneumatic booster, a master cylinder and a reservoir of fluid under low pressure which feeds the master cylinder.
Such an assembly is generally employed in the brake circuit of motor vehicles, but is, generally speaking, used to convert a force exerted on a control pedal into a fluid pressure supplying at least one fluid motor.
In a known manner, the booster of such an assembly has at least one chamber connected to a vacuum source via a non-return valve in order to maintain a vacuum in this chamber for a while after the source has dried up. The vacuum source is generally obtained by venturi effect in the region of the carburetor of the vehicle's heat engine, or alternatively it is provided by a conventional vacuum pump.
In the prior art e.g. in U.S. Pat. No. 3,013,537, the non-return valve is arranged in the booster housing in a peripheral area where the tractive forces exerted in the sheet metal of the housing are not too great. This area is, however, an area of weakness of the housing and requires a specific treatment. In addition, being arranged at the periphery of the booster housing, this valve constitutes a projecting element which may cause an obstruction owing to the general congestion in the engine compartment.
In order to free this engine compartment, it has been provided furthermore to arrange the booster in the passenger compartment of the vehicle, the booster/master cylinder assembly being fastened to the bulkhead in the region of the screws for fastening the master cylinder to the booster. In this case, the non-return valve constitutes an obvious disturbance to the passengers owing to the noises produced in obtaining and maintaining the vacuum. Moreover, it is then necessary for a tube to pass through the bulkhead.
The object of the present invention is to overcome these disadvantages by means of a compact and inexpensive assembly.
In DE-A-3 612 357, the chamber under vacuum of the pneumatic booster is connected to the vacuum source via a duct formed in the master cylinder, the non-return valve being arranged at the outlet of the duct.